Digestive System Part C + D: Pharynx, Esophagus, Stomach

Question 1

3 Phases of Swallowing

Answer 1

1. Buccal Phase
2. Pharyngeal Phase
3. Esophageal Phase

Question 2

Buccal Phase

• involuntary or voluntary?
• what happens?

Answer 2

• voluntary
• food is compacted by tongue into the “bolus”
• moves to pharynx by tongue pressing on hard palate

Question 3

Pharyngeal Phase

• involuntary or voluntary?
• what initiate swallowing reflex?

Answer 3

• involuntary

- Medulla: swallowing centre

Question 4

Esophageal Phase

• how does food move down?
• what parts do what

Answer 4

-peristalsis
Upper 1/3: somatic motor neurons to skeletal muscle
Middle 1/3: mix
Lower 1/3: PSNS (vagus) to smooth muscle

Question 5

Food can’t enter or re-enter

Answer 5

1. Mouth
2. Nasopharynx-uvula
3. Trachea-glottis + epiglottis closed

Question 6

Digestion in the stomach

Answer 6

• mechanical - churning

- chemical

Question 7

Chemical Digestion in the stomach

Answer 7

1. carbohydrates – salivary amylase until pH < 7
2. Lipids – lingual lipase (tongue), gastric lipase (chief cells) - until pH < 5-6
3. proteins – HCl (parietal cells) - denatures proteins + acts on pepsinogen (chief cells)
   - stomach protected from self-digestion by alkaline mucous (mucous cells)

Question 8

Absorption in the Stomach

Answer 8

• very little food absorbed (if any)

- some drugs (alcohol, aspirin)